Question: $ A = \left[\begin{array}{rrr}2 & 2 & 2 \\ 1 & 1 & 2 \\ 2 & 1 & 1\end{array}\right]$ What is $ A^{-1}$ ?
Explanation: $ = \left[\begin{array}{rrr}-\frac{1}{2} & 0 & 1 \\ \frac{3}{2} & -1 & -1 \\ -\frac{1}{2} & 1 & 0\end{array}\right]$